A novel fluorescent naphthalimide derivative based N-oxide chemistry for the selective detection of Fe(II) has been synthesized. The sensor N-Ox is composed of fluorophore with oxidized morpholine which can allow the deoxygenation by Fe(II), causing fluorescence turn-on with only Fe(II) except for the other metal ions. Interestingly, the enhancement of fluorescence intensity of N-Ox by adding Fe(II) was significantly activated by freezing. Accelerated fluorescence detection of Fe(II) in ice is mainly associated with freeze concentration effect that can induce a rapid kinetic response between N-Ox and Fe(II) in liquid-like-layer (LLL). In addition, confocal fluorescence microscopy images revealed that N showed a strong fluorescence signal, indicating that it was primarily localized in LLL. On the other hand, free N-Ox exhibited weak fluorescence intensity in ice. However, the fluorescence of N-Ox was dramatically enhanced upon the addition 1 equivalent of Fe(II) at the -20oC. So far, this analysis method combining N-oxide chemistry and freeze concentrate effect is the first example of fluorescent probe for Fe(II).

Enhanced fluorescence detection on ferrous ion by freezing

2019 Fall National Meeting

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